Vaporization and thermodynamics of ceramics in the Sm 2 O 3 ‐Y 2 O 3 ‐HfO 2 system

RationaleKnudsen effusion mass spectrometry (KEMS) has been a powerful tool in physical chemistry since 1954. There are many excellent reviews of the basic principles of KEMS in the literature. In this review, we focus on the current status and potential growth areas for this instrumental technique.MethodsWe discuss (1) instrumentation, (2) measurement techniques, and (3) selected novel applications of the technique. Improved heating methods and temperature measurement allow for better control of the Knudsen cell effusive source. Accurate computer models of the effusive beam and its introduction to the ionizer allow optimization of such parameters as sensitivity and removal of background signals. Computer models of the ionizer allow for optimized sensitivity and resolution. Additionally, data acquisition systems specifically tailored to a KEMS system permit improved quantity and quality of data.ResultsKEMS is traditionally utilized for thermodynamic measurements of pure compounds and solutions. These measurements can now be strengthened using first principles and model‐based computational thermochemistry. First principles can be used to calculate accurate Gibbs energy functions (gefs) for improving third law calculations. Calculated enthalpies of formation and dissociation energies from ab initio methods can be compared to those measured using KEMS. For model‐based thermochemistry, solution parameters can be derived from measured thermochemical data on metallic and nonmetallic solutions. Beyond thermodynamic measurements, KEMS has been used for many specific applications. We select examples for discussion: measurements of phase changes, measurement/control of low‐oxygen potential systems, thermochemistry of ultrahigh‐temperature ceramics, geological applications, nuclear applications, applications to organic and organometallic compounds, and thermochemistry of functional room temperature materials, such as lithium ion batteries.ConclusionsWe present an overview of the current status of KEMS and discuss ideas for improving KEMS instrumentation and measurements. We discuss selected KEMS studies to illustrate future directions of KEMS.

Section: Novel Applications Of Kemsmentioning

confidence: 99%

“…KEMS studies on the following relevant systems have recently been reported: Sm 2 O 3 ‐ZrO 2, 67,305 UO 2 ‐ZrO 2, 306 and Sm 2 O 3 ‐ZrO 2 ‐HfO 2. 244,307 …”

Section: Novel Applications Of Kemsmentioning

confidence: 99%

See 1 more Smart Citation

Knudsen effusion mass spectrometry: Current and future approaches

Jacobson,

Colle,

Stolyarova

et al. 2024

Mass spectrometric study of ceramics in the Sm₂O₃‐ZrO₂‐HfO₂ system at high temperatures

Stolyarova

Vorozhtcov

Лопатин

et al. 2021

Self Cite

Rationale Systems containing zirconia, hafnia, and rare earth oxides are indispensable in various areas of high‐temperature technologies as a basis of ultra‐high refractory ceramics. Exposure of these materials to high temperatures may result in unexpected selective vaporization of components or phase transitions in the condensed phase leading to changes in physicochemical properties. Consequently, reliable application of the ceramics based on systems such as Sm2O3‐ZrO2‐HfO2 is impossible without data on its vaporization processes and thermodynamic properties, which may be used to predict the physicochemical characteristics of the ultra‐high refractory ceramics. Methods Ceramics based on the Sm2O3‐ZrO2‐HfO2 system were obtained by solid‐state synthesis and characterized by X‐ray fluorescence and X‐ray phase analyses. The vaporization and thermodynamics of the system considered were examined by the high‐temperature mass spectrometric method using a MS‐1301 magnetic sector mass spectrometer with a tungsten twin effusion cell. Vapor species effusing from the cell were ionized by electrons with an energy of 25 eV. Results The main vapor species over the Sm2O3‐ZrO2‐HfO2 system were shown to be SmO, Sm, and O at a temperature of 2373 K, indicating selective vaporization of Sm2O3 from the samples. The partial pressures of these vapor species and the Sm2O3 activities were determined in the Sm2O3‐ZrO2‐HfO2 system and allowed the excess Gibbs energies to be evaluated. These excess Gibbs energy values were compared with the results obtained by the semi‐empirical and statistical thermodynamic approaches. Conclusions The data obtained in this study showed negative deviations from the ideal behavior in the Sm2O3‐ZrO2‐HfO2 system at 2373 K. The results calculated according to the semi‐empirical methods and statistical thermodynamic Generalized Lattice Theory of Associated Solutions were in agreement with each other. Thus, this evidenced the desirability of further experimental investigation of the Sm2O3‐ZrO2‐HfO2 system by the high‐temperature mass spectrometric method.

High‐temperature mass spectrometric study of the thermodynamic properties in the Sm₂O₃‐ZrO₂‐HfO₂ system

Каблов

Stolyarova

Vorozhtcov

et al. 2022

Self Cite

Rationale The Sm2O3‐ZrO2‐HfO2 system is a promising base for the development of a wide spectrum of new refractory materials. Reliable data on thermodynamic properties in this system are of significant importance for planning the preparation and application of high‐temperature ceramics. Especially, they can be useful for calculation of the unknown phase equilibria in this system. Methods The thermodynamic properties of the Sm2O3‐ZrO2‐HfO2 system were studied by the high‐temperature mass spectrometric method. The samples in the system under consideration synthesized by the solid‐state method were vaporized from a tungsten twin effusion cell using a MS‐1301 magnetic sector mass spectrometer. Ionization of the vapor species effusing from the cell was carried out by electrons at an energy of 25 eV. Results It was shown that, at temperatures below 2500 K, the main vapor species over the ceramics based on the Sm2O3‐ZrO2‐HfO2 system were SmO, Sm, and O corresponding to vapor composition over pure Sm2O3. The SmO, Sm, and O partial vapor pressures over the samples and the Sm2O3 activities were obtained in the temperature range 2319–2530 K. This allowed the excess Gibbs energy values to be determined. For comparison, the excess Gibbs energies in the Sm2O3‐ZrO2‐HfO2 system were also calculated by the semi‐empirical Kohler, Toop, Redlich‐Kister, and Wilson methods and optimized by the statistical thermodynamic Generalized Lattice Theory of Associated Solutions (GLTAS). Conclusions The thermodynamic data calculated by the semi‐empirical approaches at 2423 K were shown to be lower than the experimental values. However, the Toop and Wilson methods were found to be useful for evaluation of the excess Gibbs energy values at the Sm2O3 mole fraction less and higher than 0.32, respectively. The self‐consistent thermodynamic description of the Sm2O3‐ZrO2‐HfO2 system was derived at high temperatures by optimization of the experimental results using the GLTAS.